/**
 * C Implementation: grib_keys_iterator
 *
 * Description: get all the available keys in a GRIB message.
 * Example on how to use keys_iterator functions and the
 * codes_keys_iterator structure to get all the available
 * keys in a GRIB message.
 * 
 * 获取 GRIB 消息中的所有可用密钥。
 *
 */

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include "eccodes.h"

#define MAX_VAL_LEN 1024

static void usage(const char *prog)
{
    printf("usage: %s infile\n", prog);
    exit(1);
}

int sfx_grib_keys_iterator(int argc, char *argv[])
{
    int err = 0;
    int msg_count = 0;
    char value[MAX_VAL_LEN];
    size_t vlen = MAX_VAL_LEN;

    //
    if (argc != 2)
        usage(argv[0]);
    char *filename = argv[1];

    // skip read only and computed keys (跳过只读和计算键)
    // unsigned long key_iterator_filter_flags = CODES_KEYS_ITERATOR_SKIP_READ_ONLY |
    //                                           CODES_KEYS_ITERATOR_SKIP_COMPUTED;
    unsigned long key_iterator_filter_flags = CODES_KEYS_ITERATOR_ALL_KEYS |
                                              CODES_KEYS_ITERATOR_SKIP_DUPLICATES;

    // choose a namespace.
    // e.g. "ls", "time", "parameter", "geography", "statistics"
    const char *name_space = "ls";
    // name_space = NULL to get all the keys
    // char* name_space = NULL;

    FILE *f = fopen(filename, "rb");
    if (!f)
    {
        perror(filename);
    }

    codes_handle *h = NULL;
    codes_keys_iterator *kiter = NULL;
    while ((h = codes_handle_new_from_file(0, f, PRODUCT_GRIB, &err)) != NULL)
    {
        //
        msg_count++;
        printf("-- GRIB N. %d --\n", msg_count);

        kiter = codes_keys_iterator_new(h, key_iterator_filter_flags, name_space);
        if (!kiter)
        {
            fprintf(stderr, "Error: Unable to create keys iterator\n");
            break;
        }

        while (codes_keys_iterator_next(kiter))
        {
            //
            const char *name = codes_keys_iterator_get_name(kiter);
            vlen = MAX_VAL_LEN;
            memset(value, 0, vlen);
            CODES_CHECK(codes_get_string(h, name, value, &vlen), name);
            printf("%s = %s\n", name, value);

            // Alternative way of getting the string value
            CODES_CHECK(codes_keys_iterator_get_string(kiter, value, &vlen), 0);
        }

        // free memory
        codes_keys_iterator_delete(kiter);
        codes_handle_delete(h);
    }

    fclose(f);
    return 0;
}
